JP4593285B2 - Method for manufacturing a transverse element of a push belt for a continuously variable transmission - Google Patents

Abstract

The invention relates to method for producing a transverse element (10) which is intended to form part of a push belt (6) for a continuously variable transmission (1), which transverse element (10) is provided with at least one recess (8) for at least partially accommodating a support (7) of the push belt (6), the recess (8) being delimited by a supporting surface (16) for supporting the support and a side face (25) for locking the support (7) in a width direction, and the support surface (16) adjoining the side face (25) via a transition surface (60) which method comprises at least three process steps, namely: - a forming step, in which the transverse element (10) is cut out of base material (50) in plate form by means of a punching process, - a remachining step, in which the transverse element (10) is subjected to a deburring process, and - an additional processing step, in which at least the transition surface (60) of the transverse element (10) is processed.

Description

The present invention relates to a method of manufacturing a transverse element of a push belt of a continuously variable transmission.

The push belt and the transverse element of a continuously variable transmission are known. Push belts usually consist of two sets of endless continuous flat belts , also called “rings”. These endless belts function as a support for a relatively large number of transverse elements . Transverse element is movably arranged, et al is along the periphery of said ring, running, the transverse elements can transmit forces along with the movement of the push belt. In order for the pulley disk of the continuously variable transmission pulley and the transverse element to come into contact, on both sides in the width direction of the transverse element there are running surfaces that are separated in the vertical direction and intended to contact the pulley disk. Is provided. When the expressions “upper” and “lower” are used in the following description, they indicate the directions in which the contact surfaces are separated from each other from the lower part to the upper part. The longitudinal direction of the transverse element coincides with the circumferential direction of the push belt. The height direction of the transverse element corresponds to a radius direction of the push belt. The width direction of the transverse element is a direction orthogonal to both the longitudinal direction and the height direction.
The transverse element has two body surfaces. That is, the transverse element has a front surface and a back surface, and these surfaces extend substantially in parallel. Further, the front surface and the back surface are substantially orthogonal to the longitudinal direction. When viewed in the width direction, at both ends of the transverse element , recesses are provided which at least partly accommodate the ring . Each recess has a bottom surface, a top surface or a lock surface and side surfaces. The bottom surface has a support surface that supports a set of rings . The support surface is connected to the side surface of the recess through a curved transition surface . The transition surface is provided at least slightly lower than the support surface. The transverse element further has a bottom or base, a center or bridge, and an arrowhead top or top . The size of the bridge portion is smaller than the base portion in the width direction. The dimension of the arrowhead-like top is larger than the bridge when viewed in the width direction. The base consists of the contact surface and the support surface. The bridge portion includes a side surface of the recess, and the top portion includes a lock surface.

Methods for producing transverse elements are known and consist of at least two steps . The first step is a forming step , and the transverse element is cut into a plate shape from the substrate by a precise punching step. The second step is a re-machining step , and a deburring step is performed on all transverse elements . At this time, a known drum process is usually employed. The purpose of the remachining step, at the interface between two bodies faces and side between these transverse element, is to remove the burrs of the cut surface formed by the stamping process. Furthermore, Patent Document 1 discloses a third step . This third step is a step of processing the side surfaces of the recesses, and these side surfaces are further processed into curved surfaces having a relatively large radius of curvature. Such processing is performed using an abrasive belt, for example. This prevents Rukoto damage the ring when the transverse elements are in contact with the ring in the width direction.
In the actual manufacturing process, the transverse element may break unintentionally at the base. End of hand of break lines are located in the transition surface between the side surface and the support surface of the recess. Although the transverse element should be of relatively high quality and high in dimensional accuracy, the reason for the break is not clearly understood.
European Patent Application Publication No. EP-A0366169

An important object of the present invention is to provide a suitable method for manufacturing transverse elements . According to this manufacturing method, the risk of breakage can be reduced without significantly changing the design of the transverse element , in particular its dimensions. Push belt transverse element of the present invention is used, on the one hand, it is possible to transmit a larger force between the pulleys while maintaining a substantially constant life, has a longer life (fatigue resistance) on the other hand it can be, or at least there is no need to produce the same level of precision, which have the advantage that.
The present invention partially uses hypotheses based on experimental data. That is, the fracture is based on the hypothesis that Ru fatigue fracture der starting from the surface of the transition surface. According to the present invention, when the push belt is used, the after all transverse element has acts fatigue loads, because, since the clamping force to the right and left alternately by a pulley disc acts on the running surface It is. Since the pulley disk is inclined obliquely, by said clamping force, not only produces a compressive stress to the base, the notch effect originating from the transition surface, also produces a tensile stress concentrates on the curved transition surface. However, the tensile stress itself cannot explain the fracture.

According to the present invention, the rupture can be explained on the basis of the fact that another stress-increasing factor has occurred that is unexpected during operation and not previously described . The factor is elastic bending at the base. Thereby, the side part of a base will move to a longitudinal direction with respect to the center part of a base. According to the present invention, the latter phenomenon occurs because the central part is slightly thicker than the side part. That is, it is considered that the reason is that the central portion has a slightly larger dimension in the longitudinal direction. Due to the slightly larger dimensions, some play is possible between adjacent transverse elements at the side positions.
According to the present invention, Thickness of the central portion is considered to be unpredictable results caused by punching process. This has not been pointed out in the past. What this geometrical shape of the transverse element means is that the pushing force between the two transverse elements first acts on the position of the thick central part, and the transverse element and pulley disk Means that the frictional force between the two acts on the running surfaces on both sides of the base. This creates couples and a bending load acts on the transverse element . As a result, the transverse element can be bent to a position where the pushing force acts not only on the thick central part but also on the side part.
It is to be noted that the play is on the order of a few rather than very small micron. Therefore, it can be concluded that the relatively high central part is negligible. The present invention is based in part on the insight that the relatively high center is actually a very important factor in the occurrence of transverse element breakage. The reason is that the effect of the bending of the transverse element is gradually being ultimately accumulated thus bent transverse element is further bent when receiving the load engages the previous transverse element Because it ends up. The previous transverse element itself is also bent by the action of the aforementioned force . Even if a relatively small thickness of the center portion of each one of the transverse element, a transverse element which is bent a series so aligned while receiving a load of one another, the first transverse element therein considerable It will be bent by the amount.
Accordingly, the present invention proposes to reduce the risk of breakage of the transverse element by allowing the transition surface between the side surface of the recess and the support surface to withstand high loads and fatigue. According to the invention, the object can be achieved by adding an additional processing step to the known methods for producing transverse elements . This additional step is performed after at least said forming step is a step related to the processing of the transition surface.

A first option according to the invention is to apply a compressive stress to the transition surface which preferably extends to a predetermined distance in the material of the transverse element . Thus, with respect to the tensile stress generated in the position during operation, Ki out to some extent compensate the risk of fatigue cracks occur is significantly reduced.
In a detailed embodiment based on the first option of the present invention, the compressive stress is applied by a shot peening process. In the shot peening process, the transition surface is blasted with relatively small round steel grains. Compared to the case of using an angular abrasive that is generally used in known deburring and curving processes, the present invention uses small rounded steel grains, so the result of plastic deformation Internal compressive stress is generated near the surface. In order to obtain good and reproducible results, it is preferred that the hardness of the steel grains is at least higher than the hardness of the transverse elements after the end of the forming step . According to the present invention, the shot peening treatment can be carried out as a process for treating all surfaces simultaneously. This is because it has been found that process settings can be selected that have no or almost no adverse effect on the quality of the functional surface (eg, support surface or running surface ) of the transverse element . Particularly good results are obtained when the transverse element is burred after the shot peening process. In the latter case, all irregularities generated on the surface by the shot peening process can be removed by a re-machining process .
However, there is a risk that the support surface will be permanently damaged during the shot peening process. This is highly undesirable . This is because when this type of damage occurs, the life of the support portion is adversely affected, and eventually the life of the push belt is also adversely affected. To avoid this risk, in another embodiment of the first alternative of the present invention, the nitriding treatment was employed as an alternative process of machining process, proposed to impart the compressive stress by the nitriding treatment is doing. In the known nitriding process, the transverse element is placed in a hot nitrogen atmosphere. Within this atmosphere, nitrogen, went crowded melted from the surface of the transverse element to a depth of steps dependent as interstitial into the metal grid, to grant a very localized compressive stress. Such methods, a series of manufacturing processes leading to the production of push belts already encompasses a nitriding process of nitriding or ring, is advantageous in that the introduction of the second nitriding treatment is cost-effective very Good for .

The second option of the present invention for additional processing steps in the method of manufacturing the transverse element is based in part on actual test results. This test was performed to verify the validity of the hypothesis described above. According to the analysis of the test results, the correlation between the surface roughness and the fracture behavior of the transition surface was quantitatively shown by the roughness value Ra is used, for example, known in general. In the second alternative of the present invention, for example, by forming a smooth cover layer on the transition surface or by polishing the surface of the transition surface, the surface roughness values of the transition surface, said forming step It is proposed to improve the surface quality of the transition surface by making it smaller than the roughness value after the end of the process. By doing so, according to the present invention, it is possible to significantly reduce the risk of fatigue cracks generated from a heterogeneous structure of the transition surface. According to the invention, in particular in this second option , it is desirable that the additional machining step is performed only at the position of the transition plane . It is desirable that other parts / surfaces of the transverse element are not affected by the additional processing steps . The reason is that different functional requirements are imposed on other parts and surfaces of the transverse element . One example is the running surface of the transverse element . Because the running surface must efficiently transferred by friction forces between the pulleys and the belt is required minimum roughness value is the running surface.
The invention will now be described in more detail on the basis of a number of embodiments and the accompanying drawings.

(Brief description of the drawings)
FIG. 1 is a schematic side view of a continuously variable transmission having a push belt.
FIG. 2 is a front view and a side view of a transverse element used for a push belt of a continuously variable transmission.
Figure 3 illustrates more schematically the cross section of the punching apparatus known punching process for forming a transverse element from the long piece-like substrate.
Figure 4 is based on the present invention, a front view and a side view of the transverse element, schematically shows a grinding belt for machining parts of the surface of the transverse element.
Figure 5 is based on the present invention, a front view and a plan view of the transverse element, schematically illustrates a part of apparatus for processing the surface of the transverse element electrochemically.

FIG. 1 schematically shows a continuously variable transmission used in an automobile, for example, and the entire continuously variable transmission is denoted by reference numeral 1. The continuously variable transmission 1 has two pulleys 4 and 5, which are arranged on separate pulley shafts 2 and 3. An endless push belt 6 is hung on the pulleys 4 and 5 so that mechanical force can be transmitted between the pulley shafts 2 and 3. Usually, each pulley 4 and 5 has two pulley disks (not shown), and a push belt 6 is arranged between these pulley disks. When the transmission is operating, the push belt is sandwiched between the pulley and the disk, and the force can be transmitted by the frictional force between them.
The push belt 6, usually composed of a number of coaxial laminated flat belts or rings, has at least one endless support 7. The transverse element 10 is arranged over the entire circumference of the support part 7 and is movable in the circumferential direction with respect to the support part 7. For simplicity, only a few transverse elements 10 are shown in FIG. In general, the support 7 and the transverse element 10 are made of metal. In this type of transmission 1, force or rotation is transmitted between the two pulleys 4, 5, for example, by a transverse element 10 of the driving pulley of the pulley 4. The transverse element of the drive pulley is pushed into the other pulley 5 and the other pulley 5 is driven. The main role of the support 7 is to support and guide the transverse element 10.

FIG. 2 shows a front view and a side view of the transverse element 10 of the push belt 6. The main front surface of the transverse element 10 is labeled 11 and the main back surface of the transverse element 10 is labeled 12. When viewed in the vertical direction, the transverse element 10 comprises a base 13, a bridge 14 and an arrowhead-like top 15. In the base 13, an inclined zone 18 is provided on the main front surface 11. Most of the inclined zone 18 is a convex transition surface, and the two portions of the main front surface 11 are connected by a flat surface and a curved surface . Two parts of the main front is arranged to have a slight angle to each other. In the push belt, two adjacent transverse elements 10 can be inclined with respect to each other via the inclined zone 18. The base 13 has two running surfaces 17, which running surface is intended to be in contact with the pulley discs. Furthermore, a projection 21 and a recess 22 are formed in the transverse element . Most of the projections 21 of the transverse element 10 of the push belt 6 is engaged with the recess 22 of the next transverse element 10, limiting the displacement of the transverse element 10 between the adjacent.
When viewed in the width direction, concave portions 8 for accommodating at least a part of the support portion 7 are formed on both sides of the transverse element 10. Each of the two recesses 8 includes a support surface 16 that supports the support portion 7, a lock surface 9 that locks the support portion 7 in the vertical direction, and a side surface 25 that locks the support portion 7 in the width direction. A transition surface 60 is provided between the support surface 16 and the side surface 25 of the recess 8. Transition surface 60 forms a curved connecting portion between the support surface 16 and side surface 25, while, that transitions surfaces 60 on the other is provided below the supporting surface 16 located, the support surface of the support 7 holding of the center, that is, the support portion 7 so that does not begin to forced movement on the bridge section 14. The present invention specifically teaches the processing of this transition surface 60.

In order to explain the forming process , FIG. 3 schematically shows a punching process for cutting the product 51 and a punching apparatus. In this case, the product is the transverse element 10 and is cut from the flat substrate 50. The known punching device has a die 45 and a guide plate 35, and a part 52 of the base material 50 is sandwiched between the surfaces 37 and 47 during punching . The punching device further includes a cutting member 30 and a support member 40. Cutting member 30 are na the straight line supporting member 40 and the vertical direction. The peripheral shape of the cutting member 30 and the support member 40 substantially coincides with the peripheral shape of the transverse element 10 that is the object to be cut, and the cutting member and the support member cooperate with each other as the cutting member 30 moves as shown by an arrow. It moves to cut the transverse element . The support member 40 moves together with the cutting member 30 while generating a force in the direction opposite to the arrow. The cutting edges of the product 51 formed by the punching process are the running surface 17, the support surface 16, the transition surface 60, the side surface 25, and the lock surface 9 of the transverse element 10. These surfaces have a roughness value determined by the punching process.
In accordance with the present invention, it is desirable to perform another additional processing step after the forming step to allow the transverse element 10 to withstand large loads and fatigue , particularly at the location of the transition surface 60. In this regard, the present invention provides two fundamentally different approaches as additional processing steps . First, according to the present invention, a compressive stress is applied to the material of the transverse element 10 at least at the position of the transition surface 60 in the machining step . Secondly, according to the present invention, it is possible to reduce the roughness value Ra of the transition surface 60 in the processing step , which is advantageous.

A more detailed embodiment of the present invention is shown schematically in FIG. 4, in which the roughness value Ra of the transition surface 60 between the side surface 25 of the recess 8 and the support surface 16 is reduced. It has been proposed to reduce the risk of damage to the transverse element 10. To reduce the roughness value of the transition surface, or polished transition surface 60, or polishing process to smooth the transition surface 60 in other ways. By doing so, the incidence and propagation speed of fatigue cracks can be significantly reduced. According to the present invention, in such a case, a slightly modified polishing method disclosed in Patent Document 1 may be employed. This is depicted in FIG. 4 as forming the right side surface 25. That is, the side surface 25 is machined using the abrasive belt 81 using the relative movement between the side surface 25 and the belt 81. The opposite side 25 on the left side of FIG. 4 shows an improved polishing method according to the present invention. That is, the transition surface 60 is machined at the same time as the side surface 25 is machined. In order to perform such processing, the width of the grind belt 82 is at least equal to the total length of the side surface 25 and the transition surface 60.
Another approach for reducing the roughness value Ra of the transition surface 60 is to electrochemically process this surface, as schematically shown in FIG. According to this type of method, a high quality and very smooth surface can be obtained. FIG. 5 shows a portion of an apparatus 70 for electrochemical processing of the transition surface 60. This device 70 has an electrode 71 that can be inserted into the recess 8. The shape of the machining part 72 of the electrode 71 matches the shape of the transition surface 60, and the machining part 72 is moved in the vicinity of the transition surface 60. An insulating layer 73 is provided on the entire surface of the electrode 71 movable in the vicinity of the transverse element except for the surface at the position of the machined portion 72. This insulating layer prevents portions of the transverse element 10 other than the transition surface 60 from being electrochemically processed.
In order to perform electrochemical machining of the transition surface 60, the machining portion 72 of the electrode 71 is moved to the vicinity of the transition surface 60 and an electrolyte (not shown) is interposed between the machining portion 72 and the transition surface 60. Supplied to space 75. The electrode 71 and the transverse element 10 are connected to a voltage source 74. The transverse element 10 is positive with respect to the electrode 71 at least part of the processing time. Material transition surface 60 dissolves in the electrolyte under the influence of current generated through the electrolyte between the machining section 72 and the transition surface 60 of the electrode 71. Since the current is particularly concentrated in the highest part of the transition surface, smooth and high-quality surface is obtained uneven parts of the said transition surface is removed.
The electrode 71 is suitable for processing a plurality of transverse elements 10 simultaneously. FIG. 5 shows a plan view of this type of electrode 71 and shows a number of transverse elements 10 arranged next to each other. The electrode 71 is preferably provided in a fixed position and the transverse element 10 preferably passes through the electrode 71 during electrochemical processing. In a preferred embodiment of the apparatus 70 shown in FIG. 9, two electrodes 71 are used simultaneously, it is possible to simultaneously machine both sides of the transition surface 60 of the transverse element 10.

It is a schematic side view of a continuously variable transmission provided with a push belt. It is the front view and side view of the transverse element which are used for the push belt of a continuously variable transmission. Is a diagram showing more in schematic cross-section of a known stamping punching process apparatus for forming a transverse element from the long piece-like substrate. Based on the present invention, a front view and a side view of the transverse element, which is schematically shown to view the abrasive belt for machining the portion of the surface of the transverse element. Based on the present invention, a front view and a plan view of the transverse element, which is schematically shown to view a portion of an apparatus for processing the surface of the transverse element electrochemically.

1 continuously variable transmission 2, 3 pulley shaft 4,5 pulley 6 push belt
7 Endless support portion 8 Recess 9 Lock surface 10 Transverse element 11 Main front surface 13 Base portion 14 Bridge portion 15 top portion 16 Support surface 17 Running surface 18 Inclined zone
25 Side 60 Transition plane

Claims (10)

A method of manufacturing a transverse element forming part (10) of the push belt (6) for a continuously variable transmission (1), wherein the transverse element (10), the supporting portion of the push belt (6) At least one recess (8) for accommodating (7) is provided between the base (13) and the top (15) of the transverse element (10) , the recess (8) being connected to the support ( 7) the transverse surface (10) arranged between the support surface (16 ) of the base (13) supporting the base (13) and the base (13) and the top (15) for locking the support (7) in the width direction. The support surface (16) is connected to the side surface (25) via a transition surface (60).
The method
At least one forming step of cutting the transverse element (10) of a flat substrate (50) by stamping process,
Here, the punching step forms a central portion that is located at the center of the base portion (13) and is thicker than the end portion of the base portion (13) with respect to the transverse element (10),
A remachining step for deburring the transverse element (10) ;
An additional step of machining at least the transition surface (60) of the transverse element (10) ,
Compressive stress is applied to the transition surface (60) in the additional step or the surface roughness of the transition surface (60) is reduced . It said forming step is carried out prior to the additional processing step, the additional processing steps The method of claim 1, wherein the performed prior to the remachining step. The additional processing step A method according to claim 1 or 2, characterized in that it comprises a shot peening process using tinged steel globule particle a relatively small rounded. The method according to claim 1 or 2, characterized in that the additional processing step includes a nitriding treatment, and the support (7) is also nitriding. The method according to claim 1 or 2, wherein the additional processing step is characterized in that it comprises a polishing process using a polishing belt (82) for simultaneously machining the side (25) and said transition surface (60). The width of the abrasive belt is at least substantially equal to the sum of the dimensions of the side surface (25) and the transition surface (60) when viewed in the longitudinal direction of the transverse element (10). 5. The method according to 5 . The additional processing step includes an electrochemical decomposition step, wherein the electrochemical decomposition step includes:
An electrode (71) is located in the vicinity of the transition plane (60);
Supplying electrolyte to the space (75) between the electrode (71) and the transition surface (60);
The method according to claim 1 or 2, characterized in that an electric current is generated between the electrode (71) and the transition surface (60) through the electrolyte. The method of claim 7 the shape of the electrode (71), characterized in that it conforms to the shape of the transition surface (60). 3. A method according to claim 1 or 2, characterized in that the additional processing step comprises the step of forming a coating layer on the transition surface (60) of the transverse element (10). The method according to claim 9, wherein the coating layer is preferably formed by a vapor deposition method using CVD or PVD.

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